Distributor valves for use in the distribution of fluid, such as fuel for diesel engines, are generally intended to control the quantity of fuel delivered to the respective cylinders. In order to control the quantity of fuel, it is common practice to provide a spill collar around a distribution rotor to selectively control the duration of fuel injection by bypassing fuel at a predetermined time interval of the injection stroke. The rate of flow of the bypassed fuel produces cavitation both in the distributor passages and also in the supply passage. Any cavitation in the fuel system drastically effects the performance of the engine, since cavitation creates areas of voids and entrained air bubbles in the fuel system. This cavitation is primarily caused by a rapid pressure loss in the passages of the rotor once the bypassing of fuel starts thus causing the passages to overdump. The collapse of the voids and compression of the air bubbles during the next pumping stroke results in insufficient quantities of fuel being delivered to the respective cylinders during subsequent injections. Furthermore, the collapse of the cavitated areas causes erosion on the surfaces between the rotor and collar.
One attempt of overcoming this problem is to provide a relief valve in the bypass line in order to provide a back pressure in the fuel lines. The use of the relief valve helps offset the size of the voids, but it is well known that once the pressure level of the relief valve is surpassed the relief valve opens totally, thus not effectively controlling the rate of bypass flow. Even though the higher relief setting helps to control the size of the voids, the higher relief setting hampers the ability of the system to efficiently perform during idle conditions when bypass flows are high.
The present invention is directed to overcoming one or more of the problems as set forth above.